Design Optimization of Feeding Networks with a Special Size for Self-Interference Cancellation

This letter introduces an effective self-interference cancellation (SIC) for improving isolation between transmit (Tx) ports and receive (Rx) ports of an in-band full-duplex antenna with feeding networks (FNs). A significant isolation improvement is realized by replacing the traditional FNs of the antenna with SICFNs. The coupling between Tx and Rx ports is canceled in the FNs due to the specific power ratios and phase difference. Though a Python optimization procedure, the optimal values of the key parameters of the SIC FNs can be determined. To validate the proposed SIC technique, the prototype consisting of two four-element antenna arrays and four SICFNs designed with the technique is fabricated. The results of measurements performed in an anechoic chamber show an isolation improvement of 15 dB at 3.6 GHz, while only 0.3 dB gain loss for the antenna array as a sacrifice is observed.